In the passive optical network (PON) technology, an office-end optical line terminal (OLT) of an access network is connected to a user optical network unit (ONU) only by using a passive device such as a fiber or an optical splitter with no need to use an equipment room and a power supply. As shown in FIG. 1, the PON includes one OLT and a plurality of ONUs. A feeder between the OLT and the ONU is a feeder fiber; a passive optical splitter is configured to fuse a plurality of fibers; and a drop is a distribution fiber. In a PON operating process, when downstream data transmission is performed, the passive optical splitter divides one group of signals delivered by the OLT into N groups of signals, and sends them to all connected ONUs. The ONU selectively receives downstream data including an ID that is the same as an ID of the ONU. When upstream data transmission is performed, the passive optical splitter combines optical signals sent by the N groups of ONUs into one group of optical signals by using Time Division Multiple Access (TDMA), divides an upstream transmission time into several timeslots, and arranges only one ONU in each timeslot to send information as packets. Each ONU may obtain timing information from a downstream signal sent by the OLT, and then send an upstream grouping signal in a timeslot specified by the OLT, so as to avoid a conflict between ONUs. A PON based on this transmission principle is a TDM-PON.
Currently, the PON mainly includes an Ethernet passive optical network (EPON) and a gigabit passive optical network (GPON), and the EPON includes 10G EPON. As user requirements on a bandwidth become higher, a 10G bandwidth of the 10G EPON becomes increasingly insufficient, and a Next Generation Ethernet Passive Optical Network (NGEPON) begins to develop. The NGEPON is also referred to as a 100G EPON, that is, a high-speed PON. To improve the bandwidth while reducing costs, the ONU may use a 10G low-speed optical device to send and receive 25 Gbps data. However, performance of a high-speed optical signal may deteriorate when being transmitted in an existing fiber, and consequently, a bit error rate is relatively high when the optical signal is received by the ONU, thereby causing a relatively high power penalty.